Hazardous Waste Program

Missouri Risk-Based Corrective Action (MRBCA)

Vapor Pathway Subgroup

Jan. 4, 2005

Technical Memorandum to Vapor Pathway Subgroup: Update and Recommendations DOC

Attachment to the Technical Memorandum to Vapor Pathway Subgroup: Update and Recommendations:
Tier 1 Soil Type Dependent RBTLS for Petroleum Related Contaminants DOC

Attachment to the Technical Memorandum to Vapor Pathway Subgroup: Update and Recommendations:
Target Levels for Petroleum Related Contaminants XLS

Sept. 8, 2004 meeting, Jefferson City

Draft Minutes DOC

June 23, 2004 meeting

Draft Minutes DOC
Agenda DOC
Missouri Soils Data XLS
Mo. DNR memo: Ambient Benzene Concentrations in Various Airsheds


Vapor Pathway Sub-Group
Subgroup Membership DOC

At the June 23, 2004 Subgroup meeting, DNR staff agreed to perform further analysis on Tier 1 target cleanup levels for the petroleum-related chemicals. The three files below represent that analysis for three soil types:

The analysis was performed using:
a) the current default tox numbers used in the Tanks MRBCA guidance,
b) the most conservative tox numbers currently in IRIS,
c) the current default numbers for the air exchange rate, and
d) a recent EPA-recommended rate from its Vapor Intrusion Guidance.

The crack factor has been changed to 0.001 for all of the analyses (rather than 0.01 as it now appears in the Tanks MRBCA guidance).

With respect to the file names, "Change" in the title means the default inputs used to calculate the Tier 1 target levels appearing in the guidance were changed. "Default" means the inputs were not changed. "Exchange" in the title refers to the air exchange rate for a residential and a non-residential structure.

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